AML cells in contact to stromal cells with functional mitochondria increase their oxidative phosphorylation derived ATP. (A) ATP levels normalized to cell number in specified AML cell line after 1 (control condition: CC 1h) or 72 hours of MS-5-AML cocultures (CC 72h) determined by ATP bioluminescence assay. (B-C) Mitochondrial deficient MS-5 (ρ⁰ MS-5) were generated by 12-week cultures using low-dose ethidium bromide. ρ⁰ MS-5 are insensitive to (B) FCCP and (C) have a greatly impaired ATP production by mitochondria. (C-E) Luciferase-expressing AML cells were treated with oligomycin A and iodoacetate to, respectively, block oxidative phosphorylation or glycolysis, or a combination of both inhibitors. The percentage of ATP from mitochondrial oxydative phosphorylation (OXPHOS ATP) or from glycolysis (GLYCOLYSIS ATP) is displayed. (C) Mitochondrial respiration was impaired by the respiratory chain poison rotenone (10 minutes, 10 µM). (D) Percentage of OXPHOS and GLYCOLYSIS ATP in HL-60, Kasumi-1, and MOLM-14 AML cell lines after 1- or 72-hour coculture with MS-5 (CC MS-5) or p0 MS-5 or recovered from CC MS-5 and cultured in suspension for an additional 24 hours. (E) MOLM-14 cells were culture in Transwell (0.4 µm) permeable supports to prevent cell contact. (A-C,E) The experiment is representative of 3 to 5 experiments and was performed in triplicate. (D) Mean result of 5 independent experiments (^NSP > .05, *P < .1; **P < .01 ***P < .01 in a paired t test or by ANOVA).